Low-power radar system for remote detection of heartbeat and respiration using double-sideband transmission and frequency-tuning technique .

摘要

Since the 1970s, microwave Doppler radar has received more attention as a remote monitoring system on human health-care and life-sign monitoring and detection, such as physiologic movement and volume change sensing, life detection for finding human subjects trapped in earthquake rubble, cardiopulmonary monitoring for sleep apnea syndrome detection and human vital activities.;This dissertation is concentrated on the theory study, design, implementation, and measurement of the radar vital sign monitoring systems. First, challenges and limitations occurring in the realization of the vital sign monitoring systems are discussed and analyzed. It is proved that the double-sideband transmission with frequency tuning technique is a good and simple solution to resolve the null point problem and DC offset simultaneously. It is also shown that the harmonics of respiration signal occurring at high frequency may interfere with the detection of heartbeat and thus reduce its accuracy.;After that, the first Ka-band vital sign monitoring system adopting double-sideband transmission and frequency-tuning technique is illustrated. This system is built with discrete RF building blocks. This Ka-band system has been demonstrated the ability to detect heartbeat and respiration signal from a human body's four different sides and shown sufficiently high detection accuracy of over 80% at up to 2.5-m distance. Except heartbeat and respiration detection, acoustic signal has also been successfully detected by the Ka-band system. In addition, this Ka-band system demonstrated the robustness in detecting the vital sign through a thick wood board.;A portable non-contact vital sign monitoring system using 5 GHz radar is implemented for field test. The system achieved better than 80% detection accuracy at 2.8 m distance with low transmission power. The radar module and the data acquisition module are both powered by the laptop through USB connection. Meantime, by comparing three different architectures used for the 5 GHz modules, double-sideband indirect-conversion architecture showed prominent advantages over the direct-conversion architecture.;Based on the above systems, an integrated monitoring system on silicon working at 5 GHz is designed. This integrated system adopts the double-sideband transmission architecture. The whole system is still on testing. For comparison, some simulation results are given for reference.